Relapse continues to be the most likely outcome of any given attempt to quit smoking, with as many as 80-90 percent of those who attempt to quit returning eventually to smoking. Better methods for relapse prevention could significantly reduce smoking-related morbidity and mortality including cancer-related mortality. One of the strongest predictors of relapse is a single smoking episode after quitting. However, there has been little research designed to illuminate the mechanism underlying this lapse- relapse association or indeed to determine whether there is a causal relationship at all. In order to more fully understand the relationship between lapse and relapse, it is necessary to conduct systematic research. Extremely useful in this regard would be a short-term model of cessation and relapse that would allow for controlled manipulation of smoking lapse and tracking of outcomes over a relatively brief time. Such a model would significantly enhance efficiency of data gathering over that available in lengthy and expensive clinical trials designs. This project proposes to follow up on a previous study conducted in our laboratory that utilized a short-term model of cessation and relapse to investigate the effects of programmed lapses during early smoking abstinence (Chornock et al., 1992). Specifically, we propose to a) examine cessation and relapse outcomes in a simulated quit model that uses monetary incentives to slow the relapse process, b) examine experimental lapse effects in the simulated quit model and c) determine the role of nicotine exposure in effects of smoking lapse by comparing effects of exposure to nicotine-containing and nicotine free cigarettes. Overall, the project will improve our understanding of smoking relapse and the variables that influence this process. In particular, new short-term models of cessation and relapse will be developed. Further, valuable information will be obtained about the potentially powerful effects of smoking after brief periods of abstinence (lapse) using these new models.